#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	FILE *fp;


	if ((fp = fopen("test.txt", "wb")) == NULL )
	{
		printf("打开文件失败！\n");
		exit(EXIT_FAILURE);
	}

	fputc('5', fp);
	fputc('2', fp);
	fputc('0', fp);
	fputc('\n', fp);
	

	fclose(fp);

	return 0;	
}
